One of the methods of separating semiconductor wafers into individual devices or die is to scribe the wafer using a sharp object, usually a diamond tip, and then break or cleave the wafer along the scribed lines. A number of devices have been designed to carry out this breaking or cleaving process.
U.S. Pat. No. 3,687,345 describes a device to move the wafer so that the scribed line on the wafer surface is over a “breaking ridge” formed in a solid block of material. An air-powered diaphragm presses down on the top surface of the wafer. This forces the wafer down onto the “breaking ridge” which produces the bending moment required to break the wafer along the scribed line.
A device is disclosed in U.S. Pat. No. 3,790,051 wherein a wafer is placed upside down on a pliant material. A roller is pressed into the back of the wafer and as it is moved across the wafer, providing the bending force necessary to break the wafer into individual die.
In the apparatus described in U.S. Pat. No. 4,068,788, the scribe line on the surface of a wafer is aligned over the edge of a step with one row of die extending beyond the step. A shear beam is then applied to the extreme edge of the extended die providing the bending motion required to break the row of die.
U.S. Pat. Nos. 5,428,269 and 5,785,225 describe an apparatus that breaks the wafer by aligning the scribed line over a step or a blade and then rolling a wheel along the top side of the wafer to provide the bending force required to break the wafer.
The problem with all of the above-described approaches, is that some portion of the apparatus comes in contact with the top side of the wafer. There are frequently fragile structures essential to the operation of the device located at the top side of the wafer that can be damaged by contact with the apparatus.
U.S. Pat. No. 4,653,680 describes an apparatus that breaks the semiconductor wafer without, in most cases, contacting the top side of the wafer. In the apparatus a breaker arm having a knife-edge is driven into the back side of the wafer under the scribe line. In some cases, it was found necessary to place an anvil over the wafer to limit the upward travel of the wafer when it is struck by the breaker arm.
U.S. Pat. No. 5,820,006 utilizes the same general approach as that disclosed in U.S. Pat. No. 4,653,680 but discloses the use of vacuum chucks on either side of the breaking arm to prevent excessive upward movement of the wafer when it is struck by the breaking arm. While this technique allows wafer breaking without contacting the top surface of the wafer, the impact of the blade on the back of the wafer causes a very rough breaking action that results in chips being broken out along the sides of the scribe lines, and in many cases, causing damage to the device.